Entangled by his ex-girlfriend, breaking up and texting endlessly. Can this call the police? Are the police in charge?

If she seriously affects your normal life, you can call the police, and the police will certainly deal with it. However, after all, two people have been in love, so you should take time to sit down with her and talk calmly, that is, tell him what you really think and listen to her thoughts. If you have made it clear after the conversation and she still bothers you, call the police!